This invention relates to respiratory apparatus in general and, in particular, to a new and useful fresh gas device with a mixer for medical and respiration apparatus.
For the safety of patients hooked up to the respirators, either for anaesthesia or resuscitation, it must be possible to supply them with pure oxygen at any time. The need for pure oxygen can arise spontaneously due to irregularities in the circulatory conditions of the patient or due to incorrectly selected dosages of fresh gas.
West German published patent application No. DE-OS No. 22 16 222 discloses a portable apparatus for anaesthesia and respiratory resuscitation, which can be set up as a wall-mounted unit. The apparatus consists of a first part where the fresh gas, for supplying the second part with the circuits for anaesthesia and respiratory resuscitation, is being purified.
Of particular interest here is the first part, which is assembled from structural units arranged on a baseplate, to which the second part, having various treatment circuits, is connected. It contains one line for oxygen and one line for laughing gas, which lead to a gas mixing block, via an adjustable reagent feeder. For an emergency oxygen feed, there is an additional oxygen line, equipped with a valve, parallel to the other lines attached to the gas mixing block. The gas mixing block, in the direction of the gas flow, is followed by a disengageable evaporator for anaesthesia liquids, which is located upstream of a check valve, openable in the flow direction of the current, and connected to the second part. During the operating condition for anaesthesia, oxygen and laughing gas, properly metered and mixed, flow through the evaporator and there pick up the anaesthetic vapors. The fresh gas thus prepared then flows through the check valve, which prevents flow reversal, via the second part, and towards the patient. During respiratory resuscitation, proper dosages of oxygen bypass the isolated evaporator and flows toward the patient. Additional operating conditions, resulting from combinations of the two foregoing arrangements are possible.
An emergency feed supply of oxygen may be made directly through the remaining line circuit, without the reagent feeder. Disadvantages occur during this operating condition because of continuously flowing gases, in that an ill-defined oxygen supply occurs, and in that, it is necessary to turn off the evaporator. Precise oxygen supply demandes require, in addition, the switching off of the reagent feeder and, accordingly, the stopping of the flow of the laughing gas. Apart from this additional operating step, which requires time and consideration, the dosage must be changed, which then subsequently requires readjustment.